I'd definetly go for the framework approach. After building apps with and without frameworks, its a lot less painful to build upon something which exists already.

There are so many advantages to go framework, I can't tell everyone: - frameworks are (mostly) under development, so you can benefit from trends and improvements in web development

- frameworks are well tested

- frameworks are more secure. Do you have all holes for XSS etc. closed? Are you sure?

- frameworks have almost always a community behind it, so you benefit from other users knowledge and plugins

- frameworks have plugins. You don't have to write anything from scratch, like DB connections, authorization or file uploads

- frameworks have documentation. Unless you are the sole developer of your app, you really want to have good docs.

Do frameworks have disadvantages? Sure, but I don't think it outweighs the advantages.